TBL21 - Pelvic Cavity

Question 1

What separates the abdominal cavity from the bony pelvis and what is the pelvis divided into? What is the greater pelvis occupied by?

Answer 1

1) The iliac crest separates the abdominal cavity from the bony pelvis, which is subdivided by the pelvic brim into the greater pelvis and lesser pelvis
2) The greater pelvis is occupied by the inferior abdominal viscera

Question 2

What is the pelvic brim? What is the pelvic cavity continuous with?

Answer 2

1) The pelvic brim (red line) is the bony edge surrounding the pelvic inlet that opens into the lesser pelvis (aka pelvic cavity)
2) The pelvic cavity is continuous with the greater pelvis and abdominal cavity but angulated posteriorly from them

Question 3

What is the pelvic cavity bounded by? What forms the floor of the pelvic cavity?

Answer 3

1) The pelvic cavity is bounded by the hip bones, sacrum and coccyx
2) The pelvic diaphragm forms the bowl-like floor of the cavity

Question 4

What does the piriformis muscle traverse and where is its distal attachment? What is the proximal attachment of the piriformis muscle?

Answer 4

1) The piriformis muscle traverses the greater sciatic foramen to its distal attachment on the femur
2) The piriformis attaches proximally to the pelvic surface of vertebrae S2-S4

Question 5

What pads the lateral wall of the pelvic cavity? What is the levator ani and what provides its lateral attachment site?

Answer 5

1) The obturator internus muscle pads the lateral wall of the pelvic cavity
2) The tendinous arch formed by the obturator internus fascia provides the lateral attachment site for the levator ani, the broad muscular sheet forming most of the pelvic diaphragm

Question 6

What is the intermediate part of the levator ani and where does it attach anteriorly? What muscle makes up the medial part of the levator ani? What does this muscle form in this region?

Answer 6

1) The pubococcygeus muscle, the intermediate part of the levator ani, attaches anteriorly to the body of the pubis and the tendinous arch
2) The thick puborectalis muscle is the medial part of the levator ani
3) The muscle forms the puborectal sling

Question 7

What is the urogenital hiatus? What muscle forms the posterolateral part of the levator ani?

Answer 7

1) The urogenital hiatus is an anterior gap between the medial borders of the puborectalis for passage of the urethra and in females the vagina
2) The thin iliococcygeus forms the posterolateral part of the levator ani

Question 8

Where do the levator ani muscles merge and where do they attach? Is the levator ani voluntarily or unvoluntarily controlled and what is the nerve that goes to the levator ani?

Answer 8

1) The levator ani muscles merge posteriorly before attaching to the coccyx
2) The levator ani is voluntarily controlled by spinal nerve S4 (aka nerve to the levator ani)

Question 9

Why is the levator ani tonically contracted and when must it relax?

Answer 9

1) The levator ani is tonically contracted most of the time to support the abdominopelvic viscera, and to assist in maintaining urinary and fecal continence
2) The levator ani must relax to allow urination and defecation

Question 10

Which levator ani muscles are most commonly torn during childbirth and what are the consequences?

Answer 10

1) The pubococcygeus and puborectalis, the main and most medial parts of the levator ani, are the muscles torn most often
2) These parts of the muscle are important because they encircle and support the urethra, vagina, and anal canal
3) Weakening of the levator ani and pelvic fascia (e.g., tearing of the paracolpium) from stretching or tearing during childbirth, may decrease support for the vagina, bladder, uterus, or rectum, or alter the position of the neck of the bladder and the urethra
4) These changes may cause urinary stress incontinence, characterized by dribbling of urine when intra-abdominal pressure is raised during coughing and lifting, for instance, or lead to the prolapse of one or more pelvic organs

Question 11

What does the coccygeus muscle attach to? What does it provide to the levator ani?

Answer 11

1) The coccygeus muscle attaches to the deep surface of the sacrospinous ligament
2) It provides minor assistance to the levator ani in supporting the pelvic viscera

Question 12

What does the fibrous parietal pelvic fascia cover? What constitutes the visceral pelvic fascia? What fills the space between the parietal and visceral pelvic fasciae and where are these two structures continuous?

Answer 12

1) The fibrous parietal pelvic fascia covers the obturator internus and levator ani muscles
2) Adventitiae of the pelvic organs constitute the visceral pelvic fascia
3) Loose connective tissue fills the space between the parietal and visceral pelvic fasciae, which become continuous where organs penetrate the levator ani

Question 13

What suspends the organs from the lateral walls of the pelvic cavity? What suspends the uterine cervix (and vagina) from the lateral walls of the cavity?

Answer 13

1) The parietal fascia-derived lateral ligaments of the bladder and rectum suspend the organs from the lateral walls of the pelvic cavity
2) The cardinal ligament suspends the uterine cervix (and vagina) from the lateral walls of the cavity

Question 14

What does the cardinal ligament provide a passageway for and where does this passageway travel?

Answer 14

Like the lateral ligaments, the cardinal ligament provides passage to vessels and periarterial nerve plexuses from the lateral walls of the pelvic cavity to the pelvic viscera

Question 15

What are the superior and inferior gluteal arteries branches of? What is another important branch of this parent artery and what do other branches of this parent artery do?

Answer 15

1) The superior and inferior gluteal arteries are branches of the internal iliac artery
2) The internal iliac artery generates the umbilical arteries and provides branches that supply the pelvic viscera

Question 16

Where do vesicle arteries arise from and what do they supply? What do obliterated parts of the umbilical arteries form and what are these structures covered by?

Answer 16

1) Vesicle arteries, which arise from patent parts of the umbilical arteries, supply the bladder
2) The obliterated parts of the umbilical arteries form the medial umbilical ligaments, which are covered by the medial umbilical folds

Question 17

Recognize the superior hypogastric plexus, left and right hypogastric nerves, and the inferior hypogastric plexuses.

Answer 17

Look at image

Question 18

What forms the intermesenteric plexus? Where does this plexus travel? What does this plexus form and where?

Answer 18

1) Some postsynaptic sympathetic fibers with accompanying visceral afferent fibers exit the prevertebral ganglia to form the intermesenteric plexus
2) This plexus descends along the abdominal aorta
3) At the terminal bifurcation of the abdominal aorta, the intermesenteric plexus forms the superior hypogastric plexus

Question 19

What are the right and left hypogastric nerves made up of and what do they join once they enter the pelvic cavity?

Answer 19

1) The right and left hypogastric nerves are postsynaptic sympathetic fibers and visceral afferent fibers that continue from the superior hypogastric plexus
2) They enter the pelvic cavity to join the right and left inferior hypogastric plexuses

Question 20

Branches from which nerves join the inferior hypogastric plexuses? What accompanies branches of the internal iliac artery to the pelvic viscera?

Answer 20

1) Branches from the pelvic splanchnic nerves join the inferior hypogastric plexuses
2) Periarterial plexuses, derived from the inferior hypogastric plexuses, accompany branches of the internal iliac artery to the pelvic viscera